Residual compressive behavior of alkali‐activated concrete exposed to elevated temperatures

Guerrieri, Maurice; Sanjayan, Jay; Collins, Francis Gerard

doi:10.1002/fam.983

Cited by 63 publications

(32 citation statements)

References 24 publications

(44 reference statements)

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“…In contrast to the composites based on Portland cement, alkali-activated slag shows a much better performance when exposed to very high temperatures. [7][8][9] Similar to the case of Portland cement, a partial dehydration and decomposition of the binder can be observed up to 600°C. The principle changes in the microstructure of alkali-activated slag occur between 600°C and 800°C, when the dehydration of the C-A-S-H phase is complete and new phases start to crystallize, among which akermanite is dominant.…”

Section: Introductionmentioning

confidence: 56%

Effect of the aggregate type on the properties of alkali-activated slag subjected to high temperatures

Rovnanı́k¹

2015

Mater. Tehnol.

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High temperatures present a risk of destruction for most silicate-based construction materials. Although these materials are not flammable, they lose their properties due to a thermal decomposition. In contrast to ordinary Portland-cement-based materials, alkali-activated slag exhibits a better thermal stability when exposed to temperatures up to 1200°C. Due to its different porosity it is less susceptible to spalling. However, the properties of the composites after a high-temperature treatment depend also on the stability of the aggregates. The effects of two different types of the aggregate (quartz and chamotte) on the residual mechanical properties and microstructure of the alkali-activated slag mortars exposed to 200-1200°C is presented in this study. The results showed an improved mechanical performance of the thermally stable chamotte aggregate at temperatures above 600°C. a-quartz is transformed to b-quartz at 573°C, causing a volume instability and, consequently, a strength deterioration. Although chamotte also contains some quartz phase, the reaction of mullite with the alkalis from the matrix leads to the formation of albite and anorthite, making the material tougher and, thus, compensating the negative effect of quartz. Keywords: alkali-activated slag, high temperatures, chamotte, quartz, strength, microstructure Visoke temperature so tveganje za razpad ve~ine gradbenih materialov, ki temeljijo na silikatih.^eprav ti materiali niso vnetljivi, izgubijo svoje lastnosti zaradi termi~ne razgradnje. Nasprotno od materialov, ki temeljijo na portland cementu, z alkalijo aktivirane`lindre izkazujejo bolj{o temperaturno obstojnost,~e so izpostavljene temperaturam do 1200°C. Zaradi razli~ne poroznosti so manj ob~utljive za pojav lu{~enja. Vendar pa so lastnosti kompozita po visokotemperaturni obdelavi odvisne tudi od stabilnosti agregatov. V {tudiji so predstavljeni vplivi dveh razli~nih vrst agregatov (kremen in {amota) na preostale mehanske lastnosti in mikrostrukturo malte iz z alkalijo aktivirane`lindre, izpostavljene temperaturam 200-1200°C. Rezultati so pokazali izbolj{ane mehanske lastnosti toplotno stabilnega {amotnega agregata pri temperaturah nad 600°C. a-kremen se transformira pri 573°C v b-kremen, kar povzro~i volumensko nestabilnost in posledi~no poslab{anje trdnosti.^eprav {amot vsebuje nekaj kremenove faze, reagiranje mulita z alkalijami iz osnove povzro~i nastanek albita in anortita, ki povzro~ita, da material postane bolj`ilav in s tem kompenzira negativni vpliv kremena.

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Section: Introductionmentioning

confidence: 56%

Effect of the aggregate type on the properties of alkali-activated slag subjected to high temperatures

Rovnanı́k¹

2015

Mater. Tehnol.

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“…However, most of the existing data deal with the strength or spalling of small laboratory samples [14][15][16][17]. Except for the work of Rickard et al [12], Provis et al [18], Junaid et al [19][20][21][22] and Pan et al [23] on the thermal dilatation of geopolymer pastes, mortars and concrete synthesised from fly ashes of variable composition, very little is known about its deformational behaviour, creep and thermal properties of GPC.…”

Section: Nature and Characteristics Of Geopolymer Concretementioning

confidence: 99%

Deformational behaviour of fly-ash based geopolymer concrete at temperatures of up to 150°c

Junaid

2017

MATEC Web Conf.

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Abstract. The use of Geopolymer Concrete (GP * C) has been on the rise over the last few decades owing to its lower carbon emissions as compared to Ordinary Portland Cement Concrete (OPC). Recent research has also established the superior thermal properties of GPC and makes it an ideal construction material for specialized application. However, the deformational behaviour of GPC at elevated temperatures has not fully understood. If GPC is to be used as a main stream construction material for specialized applications, the exact deformational behaviour of the material under thermal loading needs to be investigated. This paper looks into the deformational characteristics of GPC (with natural crushed siliceous aggregates) when dry heated up to 150 o C at near zero loading. The deformations recorded using a clip-on extensometer are used to determine the strains developed in the GPC samples due to thermal loads. Coefficient of thermal expansion (CTE)

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“…Los valores de resistencia residual de los hormigones en estudio son menores a lo obtenido por Guerrieri et al (16) en hormigones de cemento Portland y de escoria siderúrgica activada alcalinamente expuestos a temperaturas de hasta 1.200 ºC. Las diferencias más significativas en resistencia residual de los hormigones en estudio y lo reportado en (16) se identifican a temperaturas de exposición de hasta 600 ºC; sin embargo, los valores de resistencia residual de los especímenes expuestos a 800 ºC y 1.000 ºC son comparables a lo identificado por Guerrieri et al (16).…”

Section: Relación Escoria/ (Escoria+metacaolín) / Slag/(slag+metakaolunclassified

“…Sin embargo, hay aún muchas interrogantes respecto de su desempeño y estabilidad cuando son expuestos a medios agresivos, siendo esto una de las principales limitantes para su estandarización y comercialización (8). Estudios de materiales de activación alcalina elaborados con metacaolín (9)(10)(11)(12)(13)(14) o escoria siderúrgica (15)(16)(17)(18)(19) han mostrado, que independientemente del precursor usado, generalmente estos cementantes reportan una mejorada estabilidad cuando son expuestos a temperaturas altas, comparado con el cemento Portland ordinario. Esto es más significativo en cementos alcalinos con bajos o ningún contenido de calcio, lo cual se atribuye a la formación de un gel cementante altamente polimerizado del tipo aluminosilicato sódico hidratado (4) y un contenido reducido de agua químicamente enlazada en los productos de reacción (20).…”

Section: Introductionunclassified

“…However, there are still questions regarding the performance and stability of these materials when exposed to aggressive service environments, and this is one of the main limitations facing standardisation and commercialisation of alkaliactivated materials (8). Studies of alkali-activated materials based on metakaolin (9)(10)(11)(12)(13)(14) or slag (15)(16)(17)(18)(19) have shown that independent of the precursor used, alkaliactivated cements generally show greater stability when exposed to high temperatures, compared with ordinary Portland cement. This is more remarkable in alkaliactivated cements with low calcium contents, which is attributed to the formation of a highly crosslinked sodium aluminosilicate type gel (4), and a reduced content of chemically-bonded water in the reaction products (20).…”

Section: Introductionmentioning

confidence: 99%

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Desempeño a temperaturas altas de morteros y hormigones basados en mezclas de escoria/metacaolín activadas alcalinamente

Bernal

Gutiérrez²,

Ruiz³

et al. 2012

Mater. construcc.

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RESUMENEste artículo evalúa el desempeño de morteros y hormigones basados en mezclas de escoria siderúrgica (GBFS)/metacaolín (MK), activadas alcalinamente expuestos a temperaturas altas. Se identifica una elevada estabilidad en morteros con contenidos de MK de hasta un 60% cuando se exponen a temperaturas de 600 ºC, con una resistencia residual de 20 MPa posterior a la exposición a esta temperatura. Por otra parte, la exposición a temperaturas más elevadas conduce al agrietamiento de los hormigones como consecuencia de una elevada contracción de la matriz cementante y las restricciones por efecto de los áridos, especialmente en aquellos especímenes con cementantes que contienen altos contenidos de MK. Se identifican diferencias significativas en las propiedades de absorción de agua de morteros y hormigones, y esto se relaciona con las divergencias en el desempeño de estos materiales posterior a la exposición a temperaturas altas. Esto indica que el desempeño a temperaturas elevadas de morteros de activación alcalina no es completamente transferible a hormigones, ya que los sistemas difieren en permeabilidad. Las diferencias en los coeficientes de expansión térmica entre matriz cementante y los áridos gruesos contribuyen al macrofisuramiento del material y su consecuente reducción de propiedades mecánicas.Palabras claves: cementos alcalinos, altas temperaturas, escoria siderúrgica, metacaolín, propiedades mecánicas. SUMMARYThis paper assesses the performance of mortars and concretes based on alkali activated granulated blastfurnace slag (GBFS)/metakaolin (MK) blends when exposed to high temperatures. High stability of mortars with contents of MK up to 60 wt.% when exposed to 600°C is identified, with residual strengths of 20 MPa following exposure to this temperature. On the other hand, exposure to higher temperatures leads to cracking of the concretes, as a consequence of the high shrinkage of the binder matrix and the restraining effects of the aggregate, especially in those specimens with binders containing high MK content. A significant difference is identified between the water absorption properties of mortars and concretes, and this is able to be correlated with divergences in their performance after exposure to high temperatures. This indicates that the performance at high temperatures of alkali-activated mortars is not completely transferable to concrete, because the systems differ in permeability. The differences in the thermal expansion coefficients between the binder matrix and the coarse aggregates contribute to the macrocracking of the material, and the consequent reduction of mechanical properties. . La principal diferencia entre estas dos clases de cementantes es la presencia de calcio en la escoria lo que promueve la formación de una estructura compuesta fundamentalmente por geles de silicatos cál-cicos hidratados (C-(A)-S-H) (2), mientras que en los geopolímeros se forman geles del tipo aluminosilicato sódi-co hidratado (N-A-S-H) (4). KeywordsEl uso tanto de metacaolín como de escoria activada a...

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Residual compressive behavior of alkali‐activated concrete exposed to elevated temperatures

Cited by 63 publications

References 24 publications

Effect of the aggregate type on the properties of alkali-activated slag subjected to high temperatures

Effect of the aggregate type on the properties of alkali-activated slag subjected to high temperatures

Deformational behaviour of fly-ash based geopolymer concrete at temperatures of up to 150°c

Desempeño a temperaturas altas de morteros y hormigones basados en mezclas de escoria/metacaolín activadas alcalinamente

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